Re: Fuel pressure drop
[Re: WV Runner]
#2829162
10/06/20 02:10 AM
10/06/20 02:10 AM
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Joined: Jul 2008
Posts: 610 Boise
Moparteacher
mopar
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mopar
Joined: Jul 2008
Posts: 610
Boise
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Disconnect fuel line from carb. Run hose into 5 gallon pail. Time one minute and measure fuel volume. Compare to requirements for hp and et.
If volume is low measure voltage drop to pump on positive side and then negative side at running voltage.
If you want to get really into it. you could get an oscilloscope and current ramp the pump, acquire frequency and calculate rpm, and pattern integrity. This is how we teach fuel pump diagnoses on non-race cars.
Last edited by Moparteacher; 10/06/20 02:11 AM.
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Re: Fuel pressure drop
[Re: WV Runner]
#2829271
10/06/20 12:32 PM
10/06/20 12:32 PM
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Joined: Jan 2003
Posts: 13,376 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,376
Marion, South Carolina [><]
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I use a stock tank w/ a sump welded on...no issues w/ fuel pressure.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: Fuel pressure drop
[Re: Thumperdart]
#2829279
10/06/20 12:56 PM
10/06/20 12:56 PM
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Joined: Aug 2003
Posts: 4,688 On the parachute mount
n20mstr
master
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master
Joined: Aug 2003
Posts: 4,688
On the parachute mount
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ON STOCK tanks, i always drill a hole on the bottom towards the back, and thread in a brass bushing. (3/8 internal threads whatever external) I then solder this in. Screw in a nice AN fitting 3/8 X -8 or etc, Use that as the feed your your pump. Works very well . Your fighting a lot of gravity with the stock pick up and the faster you go, the harder it is to pull the fuel up that pickup.
....BAD A$$ STREET CAR.....
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Re: Fuel pressure drop
[Re: an8sec70cuda]
#2829286
10/06/20 01:05 PM
10/06/20 01:05 PM
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Joined: Aug 2012
Posts: 65 WV
WV Runner
OP
member
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OP
member
Joined: Aug 2012
Posts: 65
WV
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I use a stock tank w/ a sump welded on...no issues w/ fuel pressure. What do you mean by sump?
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Re: Fuel pressure drop
[Re: WV Runner]
#2829288
10/06/20 01:14 PM
10/06/20 01:14 PM
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Joined: Feb 2003
Posts: 1,103 Massillon, Ohio
cudatom
super stock
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super stock
Joined: Feb 2003
Posts: 1,103
Massillon, Ohio
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Is this a replacement 3/8 seding unit and pick up? If so did you retail the sock that covers the pick up. If so this could be an issue. We had problems with higher volume pumps trying to suck the sock into the line.
Ok
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Re: Fuel pressure drop
[Re: cudatom]
#2829304
10/06/20 01:50 PM
10/06/20 01:50 PM
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Joined: Aug 2012
Posts: 65 WV
WV Runner
OP
member
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OP
member
Joined: Aug 2012
Posts: 65
WV
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Is this a replacement 3/8 seding unit and pick up? If so did you retail the sock that covers the pick up. If so this could be an issue. We had problems with higher volume pumps trying to suck the sock into the line. Yes it’s a replacement, what you mean by retail? All opened it and installed it, didn’t do anything honestly
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Re: Fuel pressure drop
[Re: WV Runner]
#2829460
10/06/20 06:27 PM
10/06/20 06:27 PM
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Joined: Feb 2003
Posts: 1,103 Massillon, Ohio
cudatom
super stock
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super stock
Joined: Feb 2003
Posts: 1,103
Massillon, Ohio
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Is this a replacement 3/8 seding unit and pick up? If so did you retail the sock that covers the pick up. If so this could be an issue. We had problems with higher volume pumps trying to suck the sock into the line. Yes it’s a replacement, what you mean by retail? All opened it and installed it, didn’t do anything honestly Sorry it should have said did you retain the sock on the pick up. My fat thumbs don't do well on phone keyboards.
Ok
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Re: Fuel pressure drop
[Re: cudatom]
#2829732
10/07/20 11:24 AM
10/07/20 11:24 AM
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Joined: Jan 2003
Posts: 13,376 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,376
Marion, South Carolina [><]
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CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: Fuel pressure drop
[Re: WV Runner]
#2830066
10/07/20 06:11 PM
10/07/20 06:11 PM
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Joined: Feb 2010
Posts: 1,645 Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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Sometimes setting the pressure high at idle results in larger drop in pressure. It depends on how the regulator is designed and the fuel pump pressure and flow rate (gals/min) relationship. A deadheaded pump is delivering close to zero gallons per minute at idle. It is going to depend on the regulator pressure and the flows and pressures it will see (ie the the pump). We took a look at a couple different regulators, and then the effect of control pressures and flow rates in this thread. https://www.forabodiesonly.com/mopa...b-stumble.437541/page-20#post-1972625252(read down from that post for pump output volume and cudafever's tests) You can probably test in a similar manner, but start with the pump data from the manufacturer. There's some basic rules of thumb for fuel consumption, and you can also look at engine dyno data for similar engines.
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